Oluwamayokun B. Adetoro

Unmanned aerial systems are increasingly deployed in low-infrastructure environments, where long-range beyond-visual-line-of-sight missions must be performed with variable payloads and across multiple operational roles. For aircraft already in service, aerodynamic improvement must often be achieved without changing the underlying architecture. In such contexts, optimisation is not an unconstrained configuration design problem, but a constrained performance-improvement problem in which geometric freedom is limited by structural, integration, and operational requirements.This paper examines aerodynamic performance improvement within existing UAV architectures operating under practical geometric and operational constraints. A structured multi-fidelity optimisation approach is applied in which low-order methods support broad wing-shape exploration while high-fidelity adjoint-based CFD is used for local fuselage refinement. The approach is motivated by the limitations of existing methods, in which low-order models do not capture local aerodynamic interactions required for meaningful refinement, while high-fidelity methods are computationally prohibitive when applied across broad design spaces. The proposed framework separates global exploration and local refinement according to the structure of the problem, combining low-order wing-shape exploration with targeted high-fidelity fuselage optimisation.The methodology is applied to the HANSARD UAV developed by UAVAid-Ltd. The optimised wing and fuselage are integrated into a final aircraft configuration and assessed using RANS simulations. At identical flight speed, the final configuration increased the lift-to-drag ratio from 13.503 to 16.09, corresponding to a 19.18% improvement relative to the baseline, primarily through increased lift. Under an equal-lift comparison, the optimised configuration maintained the baseline lift at a lower freestream velocity with a 13.81% reduction in total drag.

In this paper we present a new generalised quadratic yield function for plane stress analysis [7] for the description of the plastic anisotropy of metals and also for the study of the asymmetric behaviour in tension-compression typical of the Hexagonal Closed-Pack (HCP) materials. The new yield function has a quadratic form in the stress tensor and it simultaneously predicts accurately the r-values and directional flow stresses. It also describes very well the biaxial symmetric stress state which is fundamental for the accurate modelling of aluminium alloys. The new quadratic yield function represents the non-symmetric biaxial stress state by performing a linear interpolation from pure uni-axial loading to a biaxial symmetric stress state. The most advanced yield functions for plastic planar anisotropy characterise very well the biaxial symmetric stress region by using experimental flow stresses for the symmetric bi-axial stress state. However, the behaviour of the alloy between the uni-axial stress state and the symmetric bi-axial stress state is still not very well characterised. In this new yield function that behaviour can be assessed from interpolation from the uni-axial stress state into the symmetric bi-axial stress state until experimental yield locus fitting is achieved within a reasonable tolerance in that region. The main advantages of this new yield function is that it can be used for the modelling of metals with any crystallographic structure (BCC, FCC or HCP), it only has five anisotropic coefficients and also that it is a simple quadratic yield criterion that is able to accurately reproduce the plastic anisotropy of metals whilst using an associated flow rule. In the results and discussion we validate the yield locus for FCC and HCP alloys and we apply the new yield function in a cup drawing simulation for the assessment of the cup earing profile.

IsoGeometric Analysis (IGA) has proved to be a reliable numerical tool for the simulation of structural behaviour and fluid mechanics. The main reasons for this popularity are essentially due to: (i) the possibility of using higher order polynomials for the basis functions; (ii) the high convergence rates possible to achieve; (iii) the possibility to operate directly on CAD geometry without the need to resort to a mesh of elements. The major drawback of IGA is the non-interpolatory characteristic of the basis functions, which adds a difficulty in handling essential boundary conditions and makes it particularly challenging for contact analysis. In this work, the IGA is expanded to include frictionless contact procedures for sheet metal forming analyses. Non-Uniform Rational B-Splines (NURBS) are going to be used for the modelling of rigid tools as well as for the modelling of the deformable blank sheet. The contact methods developed are based on a two-step contact search scheme, where during the first step a global search algorithm is used for the allocation of contact knots into potential contact faces and a second (local) contact search scheme where point inversion techniques are used for the calculation of the contact penetration gap. For completeness, elastoplastic procedures are also included for a proper description of the entire IGA of sheet metal forming processes.

Isogeometric Analysis (IGA) has been growing in popularity in the past few years essentially due to the extra flexibility it introduces with the use of higher degrees in the basis functions leading to higher convergence rates. IGA also offers the capability of easily reproducing discontinuous displacement and/or strain fields by just manipulating the multiplicity of the knot parametric coordinates. Another advantage of IGA is that it uses the Non-Uniform Rational B-Splines (NURBS) basis functions, that are very common in CAD solid modelling, and consequently it makes easier the transition from CAD models to numerical analysis. In this work it is explored the contact analysis in IGA for both implicit and explicit time integration schemes. Special focus will be given on contact search and contact detection techniques under NURBS patches for both the rigid tools and the deformed sheet blank.

The aim of this benchmark is the numerical prediction of the springback of an aluminium panel used in the production of a Jaguar car. The numerical simulation of springback has been very important for the reduction of die try outs through the design of the tools with die compensation, thereby allowing for the production of dimensionally accurate complex parts at a reduced cost. The forming stage of this benchmark includes one single forming operation followed by a trimming operation. Cross-sectional profiles should be reported at specific (provided) sections in the part before and after springback. Problem description, tool geometries, material properties, and the required simulation reports are summarized in this benchmark briefing.

There are a vast number of different types of end mill tools used in the manufacturing industry, each type with a unique shape. These tool shapes have a direct influence on the cutting force it generates during machining. This article presents a more accurate approach to predicting the stability margin in machining by considering the cutting force coefficients and axial immersion angle as variables along the axial depth of cut. A numerical approach to obtaining a converged solution to the stability model is presented. The results obtained are validated using experimental results and a very good agreement is seen.